Telecommunications apparatus and method

ABSTRACT

A method of transmitting downlink data in a mobile communications system, wherein the mobile communications system comprises a base station configured to communicate wireless signals to one or more terminal devices. The method comprises receiving an indicator of a maximum number of downlink repetitions “Nmax” currently accepted by a terminal device, wherein a number of downlink repetitions indicates a number of times that the same signal is transmitted to the terminal device; setting an actual number of downlink repetitions “Ntx” so that the actual number of downlink repetitions meets the condition Ntx≤Nmax; and transmitting the downlink data, to the terminal device, wherein the downlink data is transmitted via a signal transmitted a number of times equals to the actual number of downlink repetitions.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to European Patent Application15153313.0, filed in the European Patent Office on Jan. 30, 2015, theentire contents of which being incorporated herein by reference.

BACKGROUND Field

The present disclosure relates to a method of transmitting downlink datain a mobile communications system; to a base station for transmittingdownlink data in a mobile communications system; circuitry for a basestation for transmitting downlink data in a mobile communicationssystem; a method of receiving downlink data at a terminal in a mobilecommunications system; to a terminal device for receiving downlink dataat a terminal in a mobile communications system; to circuitry for aterminal device for receiving downlink data at a terminal in a mobilecommunications system; to a method of setting a maximum number ofdownlink repetitions parameter for downlink transmissions in a mobilecommunications system; to a terminal device for setting a maximum numberof downlink repetitions parameter for downlink transmissions in a mobilecommunications system; to circuitry for a terminal device for setting amaximum number of downlink repetitions parameter for downlinktransmissions in a mobile communications system and to a wirelesstelecommunication system.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

Mobile communication systems have evolved from the GSM System (GlobalSystem for Mobile communications) to the 3G system and now includepacket data communications as well as circuit switched communications.The third generation partnership project (3GPP) has developed a fourthgeneration mobile communication system referred to as Long TermEvolution (LTE) in which a core network part has been evolved to form amore simplified architecture based on a merging of components of earliermobile radio network architectures and a radio access interface which isbased on Orthogonal Frequency Division Multiplexing (OFDM) on thedownlink and Single Carrier Frequency Division Multiple Access (SC-FDMA)on the uplink.

Third and fourth generation mobile telecommunication systems, such asthose based on the 3GPP defined UMTS and Long Term Evolution (LTE)architectures, are able to support a more sophisticated range ofservices than simple voice and messaging services offered by previousgenerations of mobile telecommunication systems. For example, with theimproved radio interface and enhanced data rates provided by LTEsystems, a user is able to enjoy high data rate applications such asmobile video streaming and mobile video conferencing that wouldpreviously only have been available via a fixed line data connection.The demand to deploy third and fourth generation networks is thereforestrong and the coverage area of these networks, i.e. geographiclocations where access to the networks is possible, is expected toincrease rapidly.

One particular area which is being developed and promoted for mobilenetworks is so-called machine type communication (MTC) applications. MTCapplications are in some respects typified by semi-autonomous orautonomous wireless communication devices (MTC devices) communicatingsmall amounts of data on a relatively infrequent basis. Examples includeso-called smart meters which, for example, are located in a customershome and periodically transmit data back to a central MTC serverrelating to the customer's consumption of a utility such as gas, water,electricity and so on. Smart metering is merely one example MTCapplication and there are many other situations in which MTC-typedevices might be used, for example for traffic surveillance,e-healthcare and general monitoring applications. In general, MTCdevices may be useful whenever there is a desire for devices tocommunicate wirelessly with some degree of autonomously (i.e. withouthuman invention). Some typical characteristics of MTC type terminaldevices/MTC type data might include, for example, characteristics suchas low mobility, high delay tolerance, small data transmissions,infrequent transmission and group-based features, policing andaddressing. Further information on characteristics of MTC-type devicescan be found, for example, in the corresponding standards, such as ETSITS 122 368 V11.6.0 (2012-09)/3GPP TS 22.368 version 11.6.0 Release 11).

It can be expected that some types of terminal device, such as MTC typeterminal devices, may be relatively low-cost devices and might need torely on battery power for extended periods. As such, it would be abenefit for such terminal devices to communicate with a base stationwhile taking battery utilisation considerations into account. It istherefore desirable to improve mobile networks to help with low powercommunications, for example for low-power MTC devices.

SUMMARY

According to a first aspect of the present disclosure, there is provideda method of transmitting downlink data in a mobile communicationssystem, wherein the mobile communications system comprises a basestation configured to communicate wireless signals to one or moreterminal devices. The method comprises receiving an indicator of amaximum number of downlink repetitions “Nmax” currently accepted by aterminal device, wherein a number of downlink repetitions indicates anumber of times that the same signal is transmitted to the terminaldevice; setting an actual number of downlink repetitions “Ntx” so thatthe actual number of downlink repetitions meets the condition Ntx≤Nmax;and transmitting the downlink data, to the terminal device, wherein thedownlink data is transmitted via a signal transmitted a number of timesequals to the actual number of downlink repetitions.

According to another aspect of the present disclosure, there is provideda base station for transmitting downlink data in a mobile communicationssystem, wherein the base station is configured to communicate wirelesssignals to one or more terminal devices. The base station is configuredto: receive an indicator of a maximum number of downlink repetitions“Nmax” supported by a terminal device, wherein a number of downlinkrepetitions indicates a number of times that the same signal istransmitted to the terminal device; set an actual number of downlinkrepetitions “Ntx” so that the actual number of downlink repetitionsmeets the condition Ntx≤Nmax; and transmit the downlink data, to theterminal device, wherein the downlink data is transmitted via a signaltransmitted a number of times equals to the actual number of downlinkrepetitions.

According to yet another aspect of the present disclosure, there isprovided a circuitry for a base station for transmitting downlink datain a mobile communications system, wherein the base station isconfigured to communicate wireless signals to one or more terminaldevices. The circuitry comprises a controller element and a transceiverelement configured to operate together to: receive an indicator of amaximum number of downlink repetitions “Nmax” supported by a terminaldevice, wherein a number of downlink repetitions indicates a number oftimes that the same signal is transmitted to the terminal device; set anactual number of downlink repetitions “Ntx” so that the actual number ofdownlink repetitions meets the condition Ntx≤Nmax; and transmit thedownlink data, to the terminal device, wherein the downlink data istransmitted via a signal transmitted a number of times equals to theactual number of downlink repetitions.

According to a further aspect of the present disclosure, there isprovided a method of receiving downlink data at a terminal in a mobilecommunications system, wherein the mobile communications systemcomprises a base station configured to communicate wireless signals toone or more terminal devices. The method comprises: obtaining a maximumnumber of downlink repetitions “Nmax” for downlink transmissions to theterminal wherein a number of downlink repetitions indicates a number oftimes that the same signal is transmitted to the terminal device;setting the value of a decoding number of repetitions for downlink data“Ndec” at a first value wherein 1≤Ndec≤Nmax; and attempting to decodedownlink data transmissions based on the decoding number of repetitionsfor downlink data.

According to another aspect of the present disclosure, there is provideda terminal device for receiving downlink data at a terminal in a mobilecommunications system, wherein the mobile communications systemcomprises a base station configured to communicate wireless signals toone or more terminal devices. The terminal device is configured to:obtain a maximum number of downlink repetitions “Nmax” for downlinktransmissions to the terminal wherein a number of downlink repetitionsindicates a number of times that the same signal is transmitted to theterminal device; set the value of a decoding number of repetitions fordownlink data “Ndec” at a first value wherein 1≤Ndec≤Nmax; and attemptto decode downlink data transmissions based on the decoding number ofrepetitions for downlink data.

According to yet another aspect of the present disclosure, there isprovided circuitry for a terminal device for receiving downlink data ata terminal in a mobile communications system, wherein the mobilecommunications system comprises a base station configured to communicatewireless signals to one or more terminal devices. The circuitrycomprises a controller element and a transceiver element configured tooperate together to: obtain a maximum number of downlink repetitions“Nmax” for downlink transmissions to the terminal wherein a number ofdownlink repetitions indicates a number of times that the same signal istransmitted to the terminal device; set the value of a decoding numberof repetitions for downlink data “Ndec” at a first value wherein1≤Ndec≤Nmax; and attempt to decode downlink data transmissions based onthe decoding number of repetitions for downlink data.

According to a further aspect of the present disclosure, there isprovided a method of setting a maximum number of downlink repetitionsparameter for downlink transmissions in a mobile communications system,wherein the mobile communications system comprises a base stationconfigured to communicate wireless signals to one or more terminaldevices. The method comprises: obtaining an upper limit “Nup” for thenumber of downlink repetitions supported by a terminal device, wherein anumber of downlink repetitions indicates a number of times that the samesignal is transmitted to the terminal device; determining, based on theupper limit, a maximum number of downlink repetitions so that themaximum number of downlink repetitions is less than or equal to theupper limit; and transmitting an indicator of the maximum number ofdownlink repetitions to a base station.

According to another aspect of the present disclosure, there is provideda terminal device for setting a maximum number of downlink repetitionsparameter for downlink transmissions in a mobile communications system,wherein the mobile communications system comprises a base stationconfigured to communicate wireless signals to one or more terminaldevices. The terminal device is configured to: obtain an upper limit“Nup” for the number of downlink repetitions supported by the terminaldevice, wherein a number of downlink repetitions indicates a number oftimes that the same signal is transmitted to the terminal device;determine, based on the upper limit and on a status of the terminaldevice, a maximum number of downlink repetitions so that the maximumnumber of downlink repetitions is less than or equal to the upper limit;and transmit an indicator of the maximum number of downlink repetitionsto a base station.

According to yet another aspect of the present disclosure, there isprovided circuitry for a terminal device for setting a maximum number ofdownlink repetitions parameter for downlink transmissions in a mobilecommunications system, wherein the mobile communications systemcomprises a base station configured to communicate wireless signals toone or more terminal devices. The circuitry comprises a controllerelement and a transceiver element configured to operate together to:obtain an upper limit “Nup” for the number of downlink repetitionssupported by the terminal device, wherein a number of downlinkrepetitions indicates a number of times that the same signal istransmitted to the terminal device; determine, based on the upper limitand on a status of the terminal device, a maximum number of downlinkrepetitions so that the maximum number of downlink repetitions is lessthan or equal to the upper limit; and transmit an indicator of themaximum number of downlink repetitions to a base station.

Further respective aspects and features are defined by the appendedclaims.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 provides a schematic diagram illustrating an example of a mobiletelecommunication system;

FIG. 2 provides a schematic diagram illustrating an LTE radio frame;

FIG. 3 provides a schematic diagram illustrating an example of an LTEdownlink radio subframe;

FIG. 4 provides a schematic diagram illustrating an example of elementsfor transmitting an LTE signal;

FIG. 5 provides a schematic diagram illustrating an example of elementsfor receiving an LTE signal;

FIG. 6 provides a schematic diagram illustrating examples of downlinkrepetition;

FIG. 7 provides a schematic ladder diagram illustrating example methodsaccording with the present disclosure;

FIG. 8 provides a schematic ladder diagram illustrating other examplemethods according with the present disclosure; and

FIG. 9 provides a schematic diagram illustrating blind decoding ofrepeated transmissions.

FIG. 10 provides a schematic diagram illustrating an example of theoperation of a terminal in accordance with the present disclosure.

FIG. 11 provides a schematic diagram illustrating another example of theoperation of a terminal in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a mobile telecommunications network/system 100operating in accordance with LTE principles and which may be adapted toimplement embodiments of the disclosure as described further below.Various elements of FIG. 1 and their respective modes of operation arewell-known and defined in the relevant standards administered by the3GPP® body, and also described in many books on the subject, forexample, Holma H. and Toskala A [1]. It will be appreciated thatoperational aspects of the telecommunications network which are notspecifically described below may be implemented in accordance with anyknown techniques, for example according to the relevant standards.

The network 100 includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (i.e. acell) within which data can be communicated to and from terminal devices104. Data is transmitted from base stations 101 to terminal devices 104within their respective coverage areas 103 via a radio downlink. Data istransmitted from terminal devices 104 to the base stations 101 via aradio uplink. The uplink and downlink communications are made usingradio resources that are licenced for use by the operator of the network100. The core network 102 routes data to and from the terminal devices104 via the respective base stations 101 and provides functions such asauthentication, mobility management, charging and so on. Terminaldevices may also be referred to as mobile stations, user equipment (UE),user terminal, mobile terminal, mobile device, terminal, mobile radio,and so forth. Base stations may also be referred to as transceiverstations/nodeBs/e-nodeBs/eNodeB, and so forth.

Mobile telecommunications systems such as those arranged in accordancewith the 3GPP defined Long Term Evolution (LTE) architecture use anorthogonal frequency division modulation (OFDM) based interface for theradio downlink (so-called OFDMA) and a single carrier frequency divisionmultiple access scheme (SC-FDMA) on the radio uplink. FIG. 2 shows aschematic diagram illustrating an OFDM based LTE downlink radio frame201. The LTE downlink radio frame is transmitted from a LTE base station(known as an enhanced Node B) and lasts 10 ms. The downlink radio framecomprises ten subframes, each subframe lasting 1 ms. A primarysynchronisation signal (PSS) and a secondary synchronisation signal(SSS) are transmitted in the first and sixth subframes of the LTE frame.A physical broadcast channel (PBCH) is transmitted in the first subframeof the LTE frame.

FIG. 3 is a schematic diagram of a grid which illustrates the structureof an example conventional downlink LTE subframe. The subframe comprisesa predetermined number of symbols which are transmitted over a 1 msperiod. Each symbol comprises a predetermined number of orthogonalsubcarriers distributed across the bandwidth of the downlink radiocarrier.

The example subframe shown in FIG. 3 comprises 14 symbols and 1200subcarriers spread across a 20 MHz bandwidth licenced for use by theoperator of the network 100, and this example is the first subframe in aframe (hence it contains PBCH). The smallest allocation of physicalresource for transmission in LTE is a resource block comprising twelvesubcarriers transmitted over one subframe. For clarity, in FIG. 3, eachindividual resource element is not shown, instead each individual box inthe subframe grid corresponds to twelve subcarriers transmitted on onesymbol.

FIG. 3 shows in hatching resource allocations for four LTE terminals340, 341, 342, 343. For example, the resource allocation 342 for a firstLTE terminal (UE 1) extends over six blocks of twelve subcarriers (i.e.72 subcarriers), the resource allocation 343 for a second LTE terminal(UE2) extends over six blocks of twelve subcarriers (i.e. 72subcarriers), and so on.

Control channel data can be transmitted in a control region 300(indicated by dotted-shading in FIG. 3) of the subframe comprising thefirst “n” symbols of the subframe where “n” can vary between one andthree symbols for channel bandwidths of 3 MHz or greater and where “n”can vary between two and four symbols for a channel bandwidth of 1.4MHz. For the sake of providing a concrete example, the followingdescription relates to LTE carriers with a channel bandwidth of 3 MHz orgreater so the maximum value of “n” will be 3 (as in the example of FIG.3). The data transmitted in the control region 300 includes datatransmitted on the physical downlink control channel (PDCCH), thephysical control format indicator channel (PCFICH) and the physical HARQindicator channel (PHICH). These channels transmit physical layercontrol information. Control channel data can also or alternatively betransmitted in a second region of the subframe comprising a number ofsubcarriers for a time substantially equivalent to the duration of thesubframe, or substantially equivalent to the duration of the subframeremaining after the “n” symbols. The data transmitted in this secondregion is transmitted on the enhanced physical downlink control channel(EPDCCH). This channel transmits physical layer control informationwhich may be in addition to that transmitted on other physical layercontrol channels.

PDCCH and EPDCCH contain control data indicating which subcarriers ofthe subframe have been allocated to specific terminals (or all terminalsor subset of terminals). This may be referred to as physical-layercontrol signalling/data. Thus, the PDCCH and/or EPDCCH data transmittedin the control region 300 of the subframe shown in FIG. 3 would indicatethat UE1 has been allocated the block of resources identified byreference numeral 342, that UE2 has been allocated the block ofresources identified by reference numeral 343, and so on.

PCFICH contains control data indicating the size of the control region(i.e. between one and three symbols for channel bandwidths of 3 MHz orgreater and between two and four symbols for channel bandwidths of 1.4MHz).

PHICH contains HARQ (Hybrid Automatic Request) data indicating whetheror not previously transmitted uplink data has been successfully receivedby the network.

Symbols in a central band 310 of the time-frequency resource grid areused for the transmission of information including the primarysynchronisation signal (PSS), the secondary synchronisation signal (SSS)and the physical broadcast channel (PBCH). This central band 310 istypically 72 subcarriers wide (corresponding to a transmission bandwidthof 1.08 MHz). The PSS and SSS are synchronisation signals that oncedetected allow an LTE terminal device to achieve frame synchronisationand determine the physical layer cell identity of the enhanced Node Btransmitting the downlink signal. The PBCH carries information about thecell, comprising a master information block (MIB) that includesparameters that LTE terminals use to properly access the cell. Datatransmitted to terminals on the physical downlink shared channel(PDSCH), which may also be referred to as a downlink data channel, canbe transmitted in other resource elements of the subframe. In generalPDSCH conveys a combination of user-plane data and non-physical layercontrol-plane data (such as Radio Resource Control (RRC) and Non AccessStratum (NAS) signalling). The user-plane data and non-physical layercontrol-plane data conveyed on PDSCH may be referred to as higher layerdata (i.e. data associated with a layer higher than the physical layer).FIG. 3 also shows a region of PDSCH containing system information andextending over a bandwidth of R344. A conventional LTE subframe willalso include reference signals which are not shown in FIG. 3 in theinterests of clarity.

The number of subcarriers in an LTE channel can vary depending on theconfiguration of the transmission network. Typically this variation isfrom 72 sub carriers contained within a 1.4 MHz channel bandwidth to1200 subcarriers contained within a 20 MHz channel bandwidth (asschematically shown in FIG. 3). As is known in the art, data transmittedon the PDCCH, PCFICH and PHICH is typically distributed on thesubcarriers across the entire bandwidth of the subframe to provide forfrequency diversity.

FIG. 4 and FIG. 5 provide schematic diagrams illustrating an example ofelements for transmitting and receiving an LTE signal, respectively.These figures correspond to the PDSCH channel. Corresponding elementsare used on the transmitter and receiver sides. On the transmitter side,an incoming bit signal has a CRC (cyclic redundancy check) calculatedand appended by CRC block 401. This signal is then encoded using a turbocoder 402 for encoding the signal for transmission and a rate matcher403 for selecting the bits to be transmitted in a given sub-frame toachieve a given code rate and/or BLock Error Rate (BLER). The ratematcher 403 can take into account HARQ reports when deciding on a coderate with a view to achieving a target BLER. The signal can then befurther processed in what has been schematically and artificiallyrepresented as a single “radio signal generator” 404 for the sake ofconciseness. This generator 404 may implement any appropriate functionssuch as scrambling, OFDM modulation, etc. The signal can then be emittedby the antenna 405.

On the receiver side, the signal will first arrive at the antenna 505and then be processed by the radio signal processor 504. The radiosignal processor 504 has also been schematically and artificiallyrepresented as a single element for the sake of conciseness and canessentially carry out the inverse functions to those carried out by thegenerator 404. The signal is then processed by the inverse rate matcher503 and the resulting bit stream is decoded by the turbo decoder 502 andforwarded to a CRC checker 501. Essentially, the CRC check checks fordata integrity of the data block that it receives as an input. Theresult of the CRC checker 501 can be used by the HARQ function forreporting errors in transmissions. In some examples, if a corrupted datablock has been identified by the CRC checker 501 and reported by theHARQ function, when the data block is transmitted again by thetransmitter and received by the receiver, the receiver can use both theoriginal and the retransmitted data blocks to try to decode theinformation. In this case, referred to as “soft combining”, the softbits (where the soft bits can for example correspond to log-likelihoodratios of the bits comprising the received modulation symbols)corresponding to the corrupted data block are not discarded but arestored instead and they can then be combined with the retransmittedsignal. This technique makes use of information received during tworeceptions of the same original data bits in order to increase thechances of arriving at a successful decoding. If the data block has beenreliably decoded, it can then be processed in the expected manner, forexample it can be forwarded to other elements for processing. Combiningof the soft bits can occur in the inverse rate matcher 503, even whenthe rate matching and modulation parameters change between transmissionof the same information bits. When the rate matching and modulationsparameters do not change between transmissions, the combining can occurin the radio signal processor 504.

It is noteworthy that for the PDCCH channel, repetition decoding canhappen in the radio signal processor 504, as the number of bitstransmitted on the PDCCH is likely to be unknown to the UE in view ofthe UE performing blind decoding of the PDCCH based on several possiblealternative hypotheses of the number of bits transmitted on the PDCCH.

FIG. 6 provides a schematic diagram illustrating examples of downlinkrepetition. In the first example 600, the number of repetitions forPDCCH/PDSCH signals is four, while the number of repetitions forPDCCH/PDSCH signals in the second example 610 is two. In these examples,the sub-frames are subsequently assigned to a PDCCH period for four ortwo sub-frames, respectively, then to a PDSCH period for four or twosub-frames, respectively, then to another PDCCH period, and so on. ThesePDCCH and PDSCH periods are defined with respect to one or moreterminals and different terminals served by the same base station mayhave different PDCCH/PDSCH periods, or may not have any repetitions.When transmitting data to a terminal using repeated sub-frames, thePDCCH period is used for repeating one or more PDCCH signals for theterminal in the resource allocation portion of the sub-frames. In theexample transmission 600, the four portions 6010 are used for repeatingthe same resource allocation signal for this terminal four times and inthe example transmission 610, the two portions 6110 (and then 6130) areused for repeating the same resource allocation signal for this terminaltwice.

Likewise, the PDSCH period is used for repeating one or more PDSCHsignals for the terminal in the data transmission portion of thesub-frames. In the example transmission 600, the four portions 6021 areused for repeating the same data transmission signal for this terminalfour times and in the example transmission 610, the two portions 6121(and then 6141) are used for repeating the same data transmission signalfor this terminal twice. Therefore, the terminal receiving this type oftransmission can decode the PDCCH section only during the PDCCH periodand the corresponding PDSCH section only during the PDSCH period forreceiving the downlink transmissions.

It is noteworthy that while one UE is decoding a PDCCH Period, anotherUE may be decoding a PDSCH period. for example, in the transmissionsshown in 600, a first UE can be receiving the PDCCH marked 6010 while asecond UE receives the PDSCH marked 6011.

In practice, when decoding a PDCCH or PDSCH signal, the terminal willreceive the first instance of the signal and if it can pass the CRCcheck, the signal will be successfully decoded. If on the other hand thefirst instance of the signal does not pass the CRC check, the terminalwill listen to the second instance of the same signal and combine thefirst and second instances and attempt to process the signal. If thecombined signal now passes the CRC check, it has been successfullyreceived. On the other hand, if it does not pass the CRC check, theterminal can listen to another instance of the signal and so on, untileither the signal is successfully decoded or the decoding has beenunsuccessful once all the instances of the signal have been transmitted.If a positive CRC check is obtained before the end of the PDCCH period,the terminal can then turn its decoder off and wait for the PDSCHperiod. Alternatively, the terminal may store all instances of thesignal received during the relevant period and, at the end of theperiod, it can combine the soft bits of the received signals and try todecode the signal based on the combined signal. When adding the softbits, the terminal can for example add the soft bits before the inverserate matcher 503, such as at the radio signal processor 504 level, andthen perform the inverse rate matching and turbo decoding and CRCchecking at the inverse rate matcher 503, turbo decoder 502 and CRCchecker 501, respectively, based on the combined signal. This method ofdecoding can be applied when the rate matching and modulation parametersare identical between transmissions. This method can be applied to boththe data channels (e.g. PDSCH) and the control channels (e.g. PDSCH).

As can be seen in the above example the “number of repetitions” as usedherein refers to the number of times that a signal is transmitted. Iffor example a signal is transmitted once, i.e. with no actual repetitionof the signal, the number of repetitions will be one. If the signal issent twice (i.e. repeated once), the number of repetitions will be two.This can be extended to a situation where a signal is not sent, whichcan then be considered to correspond to a number of repetitions of zero.It is noteworthy that this is merely a convention and that in anotherexample the number of repetitions could be defined as the number ofadditional retransmissions of the signal, such that it would set tozero, one and minus one, respectively, in the three examples justmentioned. The teachings of the present invention apply regardless ofthe convention used for counting the number of repetitions.

Repetition is useful for MTC applications. MTC devices are likely tohave simple low-power emitters and receivers and some devices areunlikely to be very mobile. Some MTC devices, such as smart meters, arelikely to be powered by a main power source, rather than by a battery.Other MTC devices, such as health monitors are likely to be mobile andbattery powered. A typical use case for repetition is the case of asmart meter which remains in the same location and which transmitsinformation such as meter readings. Such a device may for example sit atthe edge of a cell and, in poor channel conditions, may only be able toreceive transmissions when they are repeated. Each signal transmitted bythe base station would need to be transmitted multiple times before itcan be successfully decoded. Using repetitions, the base station cantransmit the same signal several times, for example 100 times, and byadding the received signals, the MTC terminal can effectively receive asignal with 100 times more energy, thereby improving the coverage forthe MTC device at the edge of the cell. The trade-off resulting fromthis technique is that the throughput that can be achieved decreases bythe same ratio that the received energy increases: when sending signalstwice, the total received energy can be doubled while the throughput ishalved. This trade-off is aligned with the needs of some MTC devices,such as smart meters, as these types of device only require lowthroughput, and the effective received energy (and hence coverage) canbe artificially increased using repetition.

In practice, for stationary MTC terminals, the number of repetitions canbe decided for example based on a power received for a singletransmission. For example, for a meter in an underground location, thesignal coverage may be poor and it may be estimated that an appropriatenumber of repetitions may be 100 while it may be determined as being 20for another meter in the same premises but in an over-ground location.Once the appropriate number of repetitions has been set, the basestation can transmit repeated signals using this number of repetitions,knowing that the channel to the UE is not changing, and the MTC devicecan decode signals knowing that the base station is repeating signalsfor this specific number of times.

This use case does not however translate very well for a conventionalnon-static terminal. For example, if the terminal is in a firstlocation, then repeating signals 100 times may not be necessary and maythus introduce a significant and unnecessary delay. On the other hand,if the number of repetitions is lowered and the terminal then moves to adifferent location, the number of repetitions may then not be enough forsuccessful decoding of transmissions and the terminal may thereforeunnecessarily waste battery attempting to decode signals with aresulting power which is too low to enable a successful decoding. Inother words, current repetitions techniques are not particularly wellsuited to non-MTC terminals which may experience significantdifficulties, in particular with respect to battery depletion, and/ordelays in receiving transmissions. It is therefore desirable to providea repetition arrangement which is better adapted to non-staticterminals.

FIG. 7 provides a schematic ladder diagram illustrating example methodsaccording with the present disclosure. The example of FIG. 7 illustrateshow a maximum number of repetitions for a terminal 701 can be set andstored by the base station 702. At the first step 711, the terminalobtains an upper limit “Nup” for the number of repetitions that theterminal 701 can support. The terminal may for example be limited byphysical aspects (such as an electronic component's capabilities, etc.),battery capacity (the UE needs to limit the number of times it repeatsreception or transmission of a signal with the goal of not depleting itsbattery resources) and/or by logical aspects (such as a softwarelimitation). An upper limit of 100 will be used in the followingdiscussions as an illustration and it will be understood that anyappropriate limitation on the number of repetitions may be used inaccordance with the present disclosure. Then, at step 712, the terminal701 determines a maximum number of repetitions “Nmax” it wishes to use.For example, terminal plugged-in to a power source and being relativelystationary may decide to use 100 as the maximum number of repetition. Ifhowever the terminal is using its battery as the sole power source andis running low on battery, the maximum number of repetitions may be setto a lower value, for example 40 or 60, such that the terminal reducesthe risk of draining its battery trying to receive transmissions. Inanother example, if the terminal is relatively mobile (i.e.non-stationary), it may estimate that having too many repetitions islikely to be counter-productive and may set the maximum number ofrepetitions value to a lower value, for example, 30, 50 or 70. Theterminal may take a variety of aspects into account. For example, it mayset the maximum number of repetitions value “Nmax” based on one or moreof: a battery status (such as a remaining battery capacity), a type ofpower source, an energy saving mode, an estimated or expected mobility,an expected level of coverage, an input received from a user, etc. Thismaximum number of repetition is used to limit the number of repetitionsused for downlink transmissions and is selected to be less than or equalto Nup, the upper limit for the number of repetitions supported by theterminal. The step 712 may be performed whenever deemed appropriate, forexample at start-up, whenever at least one of the relevant conditionschanges by a certain predetermined amount or reaches a certainpredetermined level, upon receipt from the base station 702 of a newcalculation request, following a user input, etc. A new calculation ofthe maximum number of the number of repetitions is then carried out. Forexample, if the battery charge falls below 20%, the value Nmax may bereduced by a certain amount and/or by a certain ratio.

Once Nmax has been set, the terminal 701 transmits the Nmax value, or anindicator of the value, to the base station 702 at step 713. The basestation may then store the value Nmax for this terminal for use whendownlink data is to be transmitted to the terminal 701.

FIG. 8 provides a schematic ladder diagram illustrating other examplemethods according with the present disclosure. These methods relate to abase station 802 transmitting data to a terminal 801 and to the terminal801 receiving data from the base station 802. First, at step 811, thebase station 802 detects that downlink data is to be transmitted to theterminal 801. In the illustration of FIG. 8, it is assumed that the basestation 802 already knows Nmax for this terminal but the base stationmay alternatively or additionally, obtain the Nmax value for thisterminal from a different party (such as the terminal 801 itself, a Nmaxdatabase, etc.). In other words, the base station can then obtain Nmaxfor this terminal, whether it is obtained internally or externally andat step 812, it selects an actual number of transmissions Ntx fortransmitting the data to the terminal 801. Ntx is selected to be lessthan or equal to Nmax and is based on the type of data. For example, thebase station may identify that the data to be transmitted is datarelating to an emergency message, to a public safety announcement or toa member of the user's family. In this case, the base station may decideto use a relatively high Ntx so that the terminal can be more likely todecode the data. On the other hand, if the data relates to a socialnetwork update, the data may only be transmitted at a relatively low Ntxso as to minimise the resources used for transmitting data which has alower priority. The priority of the data may be determined depending onthe service it relates to, such as a call, an emergency call, webbrowsing initiated by the user, a social media service, a radio ortelevision service, etc. Other aspects may also be taken into account,such as the delay tolerance for the data or a required or recommendedthroughput required for the data. For example, call data is not tolerantto high delays while web browsing data can support much higher delays.It may therefore be decided to use a lower Ntx for data or serviceshaving a low delay tolerance and higher Ntx for data or services havinga high delay tolerance.

In some examples the Ntx may be selected from the [1, Nmax] range whilein other examples it may be selected from the [0, Nmax] range. In thelatter case, the base station 802 could for example take the decisionthat for low priority data (e.g. social media updates), the data willnot be transmitted to the terminal 801 which corresponds to “Ntx=0”.Also, in other examples, the base station may select Ntx from one of thegroups {0, 1, Nmax}, {0, Nmax} or {1, Nmax}. As an illustration, thebase station 802 may decide either (1) to send the data using themaximum number of repetitions that the terminal 801 is currently willingto accept (“Ntx=Nmax”) if the data has a high enough priority and/ormeets the relevant conditions, or (2) not to send the data (“Ntx=0”) ifthe data does not have a high enough priority and/or does not meet therelevant conditions.

Following the selection of the Ntx at step 812, the base station 802then transmits the data by sending the corresponding signals to theterminal 801 Ntx times at step 813. In the example of FIG. 8, theterminal 801 attempts blind decoding of the data based on a number ofrepetitions less than or equal to Nmax at step 814. Blind decoding isfurther discussed below in particular in respect of FIG. 9. In otherexamples the terminal 801 may simply attempt to decode the transmissionsbased on a number of repetitions less than or equal to Nmax. At the endof step 814, the terminal 801 can reach a conclusion that the datatransmitted by the base station 802 at step 813 has been successfullydecoded or could not be decoded, e.g. based on the CRC result calculatedby the receiver's CRC checker 501.

Accordingly, a terminal can receive data that has been transmitted anumber of times which depends on a maximum number of repetitions thatthe terminal will accept and based on the type of data to betransmitted. As a result, the amount of repetition can be tailored tothe terminal and/or data.

FIG. 9 provides a schematic diagram illustrating blind decoding ofrepeated transmissions in accordance with an aspect of the presentdisclosure. In this example, the resource allocation messages (in thePDCCH section of the sub-frames) are repeated up to four times and thedata messages (in the PDSCH section of the sub-frames) are repeated upto four times as well. In other words both the PDCCH period and thePDSCH period correspond to four sub-frames, i.e. 4 ms in LTE. Asdiscussed above in respect of FIG. 6, the PDCCH sections 910 of thePDCCH period are used to transmit allocation messages to the terminalwhich will not decode the PDSCH sections 911 of this period, and thePDSCH sections 921 of the PDSCH period are used to transmit datamessages to the terminal which will not decode the PDCCH sections 920 ofthis period. In the case where the terminal does not know the actualnumber of repetitions used by the base station for the transmissions,the terminal can carry out blind decoding to attempt to decode thetransmissions whilst not know the number of repetitions. The terminalcan attempt to decode the transmissions assuming a certain number ofrepetitions has been used and, if the decoding is unsuccessful, attemptto decode the transmissions assuming a different number of repetitions.For the sake of clarity, the assumed number of repetitions used by theterminal when attempting to decode the downlink transmissions will bereferred to as “Ndec”. In the example of FIG. 9, the terminal knows theNmax value and thus knows that any transmissions it receives have beentransmitted (or repeated) a number of times between 1 and Nmax (1 andNmax included) where Nmax=4 and, in this particular example, the numberof repetitions used can only be a multiple of two, i.e. only values 1, 2and 4 could have been used by the base station. First, the terminal willtry to decode the PDCCH section for Ndec=1 with a view to identifyingany resource allocation messages for this terminal in the PDCCH sectionsfor each of the sub-frames 950-953. If the terminal can successfullydecode any of the resource allocation messages, it will then attempt todecode the PDSCH section for each of the sub-frames 954-957, where aresource allocation message in sub-frame 950, 951, 952 or 953corresponds to allocated resources allocated in sub-frame 954, 955, 956or 957, respectively. In the event that the terminal is unable to decodethe transmissions when assuming Ndec=1 (for example unable to decode therelevant PDCCH transmissions), the terminal can increase Ndec to thenext possible value, in this case Ndec=2 and try again. In this example,this would result in the terminal attempting to decode the PDCCHsections assuming repetition of the signals in the first pair 960 ofsub-frames and in the second pair of sub-frames 961. If resourceallocation messages are successfully decoded in pairs 960 and 961, theterminal will attempt to decode the corresponding allocated resources.In this example, the terminal will attempt to decode the PDSCH sectionsin corresponding pairs of sub-frames 962 and 963. Likewise, if thisattempt is unsuccessful, the terminal will attempt to decode the PDCCHsection assuming Ndec=4, the last possible Ndec value and, if a correctCRC is found at this decoding stage, the terminal will attempt to decodethe corresponding allocated resources in the PDSCH section of the group971 of four sub-frames. The terminal can thus decode downlinktransmissions sent using repetition even though it does not know inadvance the actual number of repetitions used for sending thetransmissions.

In the example of FIG. 9, the terminal starts with Ndec=1 for decodingthe PDCCH increasing to Nmax via each possible value every time thedecoding is unsuccessful. However, in other examples, the terminal maytry with various Ndec values in any order. For example, the terminal canstart with Ndec=Nmax and gradually decrease the value of Ndec afterunsuccessful attempts, or may try in any other order. It is alsonoteworthy that when a reference is made to an unsuccessful decoding,this failure to decode the signals could be identified if either signalsare being communicated to the terminal but have been received in acorrupted form (e.g. the CRC check is negative) or if no signals havebeen communicated to the terminal such that no data with a positive CRChas been decoded. In other words, an unsuccessful decoding will coverall cases but successful decoding cases (where a positive CRC isobtained).

FIGS. 10 and 11 illustrate an example of the operation of a terminal inaccordance with the present disclosure. In both cases, the maximumnumber of repetitions for the PDCCH and the PDSCH is set to 2 and thebase station is operable to configure the repetition of signals based onthe type of traffic, and in particular dependent on whether the incomingtraffic relates to emergency services (where an “emergency service”could be related to a traditional emergency service, such as a policenotice, tsunami warning etc., or could be related to a high priorityservice, such as a parent attempting to find a lost child). In the caseof FIG. 10, the base station receives downlink traffic relating to anemergency call while, in the case of FIG. 11, the base station receivesdownlink traffic relating to a social media update. The base stationknows that the terminal is capable of receiving repeated signals and hasindicated different maximum number of repetitions for the two traffictypes. For example it has indicated Nmax=2 for the emergency servicesand Nmax=1 for the social network updates. Alternatively, the UE couldjust signal Nmax=1 for the social network updates and it would beunderstood by both the base station and the terminal that emergencyservices can use any number of repetitions up to a maximum defined inthe specifications. The base station can then decide on the actualnumber of repetitions to use for downlink transmissions based on thetype of traffic and any other suitable parameter, such as channelconditions. In the case of FIG. 10, the downlink data relates to anemergency call such that it is likely to be assigned the highestpriority level. The base station can then transmit the data to theterminal using a repetition of 2; in this case the same amount ofrepetition is applied for both the PDCCH and PDSCH messages. Thus, forthe sub-frames 1001 and 1002 of the first PDCCH period, the base stationtransmits resource allocation information to the terminal, wherein thesame resource allocation signals are transmitted in sub-frames 1001 and1002. As this is a PDCCH period, the terminal will have its receiverturned on so that it can listen to communications in the PDCCH sectionfor any messages addressed to it. Then, during the first PDSCH periodconsisting of sub-frames 1003 and 1004, the base station transmits theemergency call data to the terminal, with a repetition of 2. That is,the same data signals are transmitted in sub-frames 1003 and 1004. Onthe receiving side, the terminal is aware from the resource allocationreceived at sub-frames 1001 and 1002 that it is expecting data in thenext PDSCH period and it will thus keep its receiver on for sub-frames1003 and 1004. It will then attempt to decode the data transmission sentvia sub-frames 1003 and 1004. On the other hand, if the base station nolonger has downlink data to transmit to the terminal, it will notallocate resources to the terminal for the next PDSCH period and willtherefore not include any allocation information for this terminal inthe next PDCCH period consisting of sub-frames 1005 and 1006. As aresult, the terminal will not expect any data in the PDSCH periodconsisting of sub-frames 1007 and 1008 and will therefore turn itsreceiver off for this PDSCH period, thereby saving power and thusreducing battery utilisation.

In the example of FIG. 11, the incoming downlink data relates to asocial network update. This type of traffic is unlikely to relate to ahigh priority services and can thus be given a low priority, for exampleby way of attributing a low priority index to the traffic. The basestation, knowing that the type of traffic is of a low priority, can thendecide not to transmit the data to the terminal, if the terminal is inchannel conditions that would require large amounts of repetition (inthis example, 2 repetitions are considered to be a “large amount”, forthe sake of simplicity of the figures). In other words, the base stationwill not include any resource allocation message in the PDCCH forsub-frames 1101 or 1102 (PDCCH period) and will not include any data inthe PDSCH for sub-frames 1103 and 1104 (PDSCH period) as it wouldnormally be expected to do. On the receiving side, the terminal will notfind any resource allocation message in the PDCCH of sub-frames 1101 and1102 such that it will not expect to receive any data in the PDSCH ofsub-frames 1103 and 1104 and will thus be able to turn its receiver offfor the entire duration of the next PDSCH period. As the base station nolonger has any data to transmit to the terminal, the description of theoperation of the base station and of the terminal for sub-frames1105-1108 corresponds to that of sub-frames 1005-1008 of FIG. 10. Thediscussion of these sub-frames will thus not be repeated herein, for thesake of conciseness.

As can be seen for the discussion of FIGS. 10 and 11, by adapting thenumber of repetitions to the type of traffic and based on a number ofrepetitions that has been indicated by the terminal, energy savings canbe achieved.

There has therefore been provided an arrangement where the number ofrepetitions to be used for transmitting or receiving downlink data canbe tailored or selected based on a maximum number of repetitions thatthe terminal will accept and on any other relevant parameter, such asthe type of traffic to be transmitted or the battery depletion status ofthe terminal. Accordingly, the terminal can decode PDCCH up to themaximum repetition level that the UE can tolerate for any application.The base station will only schedule the UE with repetition levels thatare commensurate with the priority of the application. Since the UEdecodes PDCCH up to the maximum repetition level, it can always decodePDCCH relating to important applications. It can turn its receiver offduring the “PDSCH period” if it is not scheduled. Compared to anarrangement where the maximum number of repetition Nmax is notcommunicated to the base station, the base station will attempt totransmit to the UE with large numbers of repetitions even when the UE isnot able to decode those transmissions. In doing so, the base station'srate control function (such as a function that attempts to determine theappropriate number of repetitions to apply for transmissions to a UE)will not be able to function correctly

The base station rate control function is traditionally used todetermine a modulation and coding rate to be used in DL transmissions(see for example the discussion of rate control in R1-124517 [7]), butcan be straightforwardly adapted to determine the number of repetitionsto be used for DL transmissions. In the rate control function, the basestation decides on the amount of coverage extension to apply using aclosed loop monitoring process: if the there is no response from theterminal or if a response is received indicating that the base station'stransmission was not received by the UE (either of these cases areindications of failure of the transmission to the terminal device), thebase station tries more repetition and if there is a response from theterminal (indicating that the base station's transmission was receivedby the UE: an indication of success of the transmission to the terminaldevice), the base station tries using less repetition. If the terminalthen decides that it is no longer going to receive more than apredetermined number of repetitions Nmax which is for example lower thanthe value assumed by the base station and it does not inform this valueof Nmax to the base station:

-   -   When the base station does not receive a response from the        terminal, or a response indicating NACK (negative        acknowledgement) for a certain number of repetitions, it will        try to send the data again with an increased amount of        repetition applied.    -   The terminal will still not respond to the new transmission as        the number of repetitions is too high for the terminal to        receive it.    -   The base station performs the above increase in the amount of        repetition until the maximum number of repetitions that the base        station is designed to apply is reached.

Such a mode of operation will waste physical resources in the networkwithout achieving an actual transmission of data to the terminal and istherefore not desirable.

In the present disclosure, when a reference is made to a terminaldecoding a PDCCH or PDSCH section, as the skilled person willunderstand, the terminal may only be attempting to decode part of thePDCCH or PDSCH, respectively. For example, the terminal may only try todecode the resources elements of the PDSCH which have been allocated tothe terminal (via the PDCCH).

Even though in the above description of the figures the same number ofrepetitions has been used for the PDSCH signals and for the PDCCHsignals, in other examples different number of repetitions can be usedfor these channels. This applies to the upper limit, maximum and/oractual number of repetitions for the terminal. The maximum number ofrepetitions for PDCCH signals (“Nmax-ra”) and for the PDSCH signals(“Nmax”) can be communicated together or separately to the base station.In one example, the PDSCH repetitions can have a maximum of 10repetitions and the PDCCH repetitions can have a maximum of 20repetitions. As a result, the PDSCH period would be of 10 ms and thePDCCH period would be of 20 ms. Also, in the blind decoding example ofFIG. 9, for a successful decoding of the PDCCH at a number ofrepetitions Ndec-ra, the same number of repetitions was assumed fordecoding the PDSCH (“Ndec”). However in other examples Ndec may bedifferent from the number Ndec-ra for successfully decoding the PDCCH.In some cases, there may be a ratio between Ndec and Ndec-ra, which mayalso correspond to a ratio between Nmax and Nmax-ra.

It is noteworthy that even though the present disclosure has beendiscussed in the context of LTE, its teachings are not limited to LTE orto other 3GPP standards and, in particular, even though the terminologyis the same or similar to that of the LTE standard, the teachings arenot limited to the present version of LTE and could apply equally to anyappropriate arrangement not based on LTE and/or compliant with any otherfuture standard. For example, any discussion of PDCCH and PDSCH sectionscan be understood to relate more generally to any resource allocationsmessage and data message portions of a transmission. Additionally, inother examples the transmissions may not be designed to include separateallocation and data portions to be decoded separately and/or may notinclude any resource allocation portion at all.

In the above examples, the repetition periods have been formed ofconsecutive sub-frames and the periods are themselves adjacent to oneanother. In other examples, the periods may be arranged differently. Forexample, a repetition period for repeating the same signal may be formedof non-adjacent sub-frames and the periods may not be adjacent. Forexample, in the example of FIG. 10, the PDCCH period may consist ofsub-frames 1001 and 1003, the PDSCH period may consist of sub-frames1005 and 1006 and the next PDCCH period may consist of sub-frame 1008and of another sub-frame, not represented on FIG. 10 but which wouldhave been allocated number 1010 using the sub-frame numbering of thisfigure.

In the present disclosure, the decision regarding the number ofrepetitions to use for the downlink transmission has generally beendescribed as being made by the base station. While this is fully withinthe scope of the present disclosure, in other examples, this decisioncould also be made by another entity or element which then informs thebase station of the Ntx to use for the downlink transmission to theterminal. The base station would then simply execute the transmission inaccordance with the decision made by the other entity.

The different numbers of repetitions to use for downlink transmissions,regardless of the transmission being of a resource allocation messagefor transmitting data or to the transmission of the data, can take anyappropriate value. For example, in some cases Nmax can be selected fromany of the following (non-exhaustive) list of sets of values: the [0,Nup] range of naturals, the {0, Nup} set, {Nup}, any power of two in the[0, Nup] range, the {0, 1, Nup} set, etc., or any combination thereof.Likewise, the Ntx value can be selected from any of the following(non-exhaustive) list of sets of values: the [0, Nmax] range ofnaturals, the {0, Nmax} set, {Nmax}, any power of two in the [0, Nmax]range, the {0, 1, Nmax} set, etc., or any combination thereof. It isalso within the scope of the present disclosure that Nmax may take “1”as a value, if appropriate.

Additionally, whereas in some cases the terminal can carry out blinddecoding for every possible Ndec value in the [1, Nmax] range, in othercases the terminal will only attempt to decode the downlinktransmissions for a limited subset of Ndec values (e.g. as illustratedin FIG. 9), or for a single Ndec value such as Ndec=Nmax. If for examplethe base station is configured to select Ntx is from the {0, Nmax} set,where Nmax is set by the terminal, the terminal will either not receivedownlink data, or receive it with a Nmax repetition. The terminal canthen attempt to decode all incoming signals assuming an Nmax repetitiononly.

According to the present disclosure, the repetition numbers are specificto a terminal such that two terminals served by the same base station donot necessarily use the same repetition number. Likewise, the repetitionperiods, such as the PCCCH and PDSCH periods discussed herein, can havedifferent durations for different terminals and/or can start atdifferent times for different terminals.

Additionally, even though in the discussion of the examples above onlyone value of the maximum repetition number for a terminal has beendiscussed, in other cases the terminal could select and indicate two ormore maximum numbers of repetitions. For example, in a system wheretraffic is classified based on a priority level selected from 1 to 5,the terminal could select and indicate a first maximum number ofrepetitions for traffic with a priority level of 4 or 5 and a secondmaximum number of repetitions for traffic with a priority level of 3 orless. For example, the terminal may be willing to have more repetitionfor high priority traffic with a view to increasing the chances ofsuccessfully receiving the traffic, at the expense of battery powerconsumption, and to have less repetition for lower priority traffic,which is less critical.

In addition to the type of traffic, the number of repetitions Ntx may beselected based on a terminal-specific configuration. For example, theterminal may be associated with a setting such that either repetition isused with Nmax, or no traffic is to be sent. Such a terminal-specificconfiguration may be set or stored at the terminal and/or the basestation. For example, some types of lower priority traffic may beallocated Ntx=0 by the base station so that it is not transmitted to theterminal. Such a comparison of Nmax with Nup may involve transmittingthe Nup number to the base station, if appropriate, or in other cases,Nup can be retrieved from a database. In this case, Nmax can be comparedto one or more fractions of Nup, for example 80% of Nup and 40% of Nupso at to achieved a better granularity in response to the value at whichNmax has been set.

This may also be generalised and the Ntx may be derived from acomparison between Nmax and a reference number of repetitions “Nref”. Iffor example Nup=100 and Nref=80, then a Nmax set to 90 could result in adifferent Ntx for the downlink transmissions than if Nmax is for example70. The previous example can be viewed as the specific example use ofthe parameter Nref, where Nref is set with respect to Nup.

The type of data may be identified based on the service or applicationrequesting the transmission. For example if the data relates to anemergency service, it may be treated differently than if it relates to avideo service. The type of data may be identified from an Access PointName (APN), also called PDN Identity, or any other type of existingidentifier or messages. Additionally or alternatively new identifiersmay be used when identifying the type of data to be transmitted. Forexample the base station may be able to allocate a priority number tothe traffic based on an inspection of at least part of the packet so asto determine what the traffic relates to. Any other suitable type ofclassification may be used in accordance with the present disclosure.

The number Nmax, and any other number of repetitions that may betransmitted by the terminal to the base station may be communicated inany appropriate manner. In some cases, the terminal may use explicitsignalling, for example including an indicator for Nmax in RRCsignalling to the base station and/or use differential signalling, forexample indicating that Nmax can be increased or decreased. Thedifferential signalling may in some examples includes only an “up” or“down” indication and the terminal and base station may know by how muchto increase or decrease the value of Nmax. Optionally, the “up” or“down” indication may also in some or all cases include an indication ofthe difference between the previous value for Nmax and the new value forNmax. For example, the terminal may send differential signallingindicating “−20” where the minus sign indicates that the Nmax should bedecreased and “20” that it should be decreased by 20. In anotherexample, the terminal may use a “not received” indicator. While ACK/NACKsignalling indicates that a user has successfully or unsuccessfully,respectively, received data on a PDSCH, the new “not received”signalling may indicate that the terminal has not attempted to receiveor decode the PDSCH. This signalling may be used as an indication todecrease the maximum number of repetitions applied by the base station,for example because the terminal decided not to attempt to receive thePDSCH with a view to saving battery.

As used herein, the expression “greater than” is intended to explicitlycover both “greater than or equal to” and “greater than but not equalto”. Likewise, the expression “less than” is intended to explicitlycover both “less than or equal to” and “less than but not equal to”.

As used herein, transmitting information or a message to an element mayinvolve sending one or more messages to the element and may involvesending part of the information separately from the rest of theinformation. For example, if measurement configuration information sentby a base station to a terminal includes an identification of inactivechannels to monitor and of active channels that can be used forgenerating measurement results for the inactive channels, the inactivechannel(s) identification information may be sent in a first message (ora first group of messages) and the active channel(s) identificationinformation may be sent separately in a second message (or second groupof messages). The base station may later update the active channel(s)identification information without updating the inactive channel(s)identification. All of these example communications are thus intended tobe covered as examples of “transmitting (this type of) measurementconfiguration information” to the terminal.

Further particular and preferred aspects of the present invention areset out in the accompanying independent and dependent claims. It will beappreciated that features of the dependent claims may be combined withfeatures of the independent claims in combinations other than thoseexplicitly set out in the claims.

Thus, the foregoing discussion discloses and describes merely exemplaryembodiments of the present invention. As will be understood by thoseskilled in the art, the present invention may be embodied in otherspecific forms without departing from the spirit or essentialcharacteristics thereof. Accordingly, the disclosure of the presentinvention is intended to be illustrative, but not limiting of the scopeof the invention, as well as other claims. The disclosure, including anyreadily discernible variants of the teachings herein, defines, in part,the scope of the foregoing claim terminology such that no inventivesubject matter is dedicated to the public.

Respective features of the present disclosure are defined by thefollowing numbered paragraphs:

Clause 1. A method of transmitting downlink data in a mobilecommunications system, wherein the mobile communications systemcomprises a base station configured to communicate wireless signals toone or more terminal devices, the method comprising:

-   -   receiving an indicator of a maximum number of downlink        repetitions “Nmax” currently accepted by a terminal device,        wherein a number of downlink repetitions indicates a number of        times that the same signal is transmitted to the terminal        device;    -   setting an actual number of downlink repetitions “Ntx” so that        the actual number of downlink repetitions meets the condition        Ntx≤Nmax; and    -   transmitting the downlink data, to the terminal device, wherein        the downlink data is transmitted via a signal transmitted a        number of times equals to the actual number of downlink        repetitions.

Clause 2. A method according to clause 1 wherein the setting of theactual number of downlink repetition is, based on the type of downlinkdata to be transmitted to the terminal device.

Clause 3. A method according to clause 2 wherein the type of downlinkdata comprises a priority level for the downlink data.

Clause 4. A method according to clause 2 or 3 wherein the type ofdownlink data is at least partially derived from the type of service orapplication requesting the data transmission.

Clause 5. A method according to any of clauses 1 to 4 comprising:

-   -   retrieving a reference number of downlink repetitions for the        terminal device,    -   wherein the setting of the actual number of downlink repetitions        is based on a comparison between the maximum number of downlink        repetitions “Nmax” currently accepted by a terminal device and        the reference number of downlink repetitions.

Clause 6. A method according to any of clauses 1 to 5 wherein thesetting of the actual number of downlink repetitions comprises:

-   -   deciding whether to transmit the downlink data to the terminal        device based on the type of downlink data;    -   if it is decided to transmit the downlink data, setting the        actual number of downlink repetitions so that it meets the        condition 1≤Ntx≤Nmax; and    -   if it is decided not to transmit the downlink data, setting the        actual number of downlink repetitions to zero.

Clause 7. A method according to any of clauses 1 to 6 wherein the basestation is configured to communicate wireless signals to the one or moreterminal devices in a series of time sub-frames, wherein sub-framescomprise a first section for resource allocation and a second sectionfor data transmission and wherein transmitting the downlink data to theterminal device comprises:

-   -   transmitting a resource allocation message for the downlink data        and for the terminal device via a first set of one or more        sub-frames in the first section; and    -   subsequently transmitting the downlink data in a second set of N        sub-frames in the second section wherein N is the actual number        of repetitions.

Clause 8. A method according to clause 7 wherein the sub-frames aregrouped in a first time period for repeating resource allocation signalsand in a second time period for repeating data signals and wherein

-   -   the first set of one or more sub-frames consists of adjacent        sub-frames starting at the start of the first time period; and    -   the second set of one or more sub-frames consists of adjacent        sub-frames starting at the start of the second time period.

Clause 9. A method according to clause 7 or 8, wherein the first set ofone or more sub-frames consists of N sub-frames.

Clause 10. A method according to any of clauses 1 to 9 wherein theactual number of downlink repetitions is set based on indications ofsuccess for past transmissions to the terminal device.

Clause 11. A base station for transmitting downlink data in a mobilecommunications system, wherein the base station is configured tocommunicate wireless signals to one or more terminal devices, the basestation being configured to:

-   -   receive an indicator of a maximum number of downlink repetitions        “Nmax” supported by a terminal device, wherein a number of        downlink repetitions indicates a number of times that the same        signal is transmitted to the terminal device;    -   set an actual number of downlink repetitions “Ntx” so that the        actual number of downlink repetitions meets the condition        Ntx≤Nmax; and    -   transmit the downlink data, to the terminal device, wherein the        downlink data is transmitted via a signal transmitted a number        of times equals to the actual number of downlink repetitions.

Clause 12. Circuitry for a base station for transmitting downlink datain a mobile communications system, wherein the base station isconfigured to communicate wireless signals to one or more terminaldevices and wherein the circuitry comprises a controller element and atransceiver element configured to operate together to:

-   -   receive an indicator of a maximum number of downlink repetitions        “Nmax” supported by a terminal device, wherein a number of        downlink repetitions indicates a number of times that the same        signal is transmitted to the terminal device;    -   set an actual number of downlink repetitions “Ntx” so that the        actual number of downlink repetitions meets the condition        Ntx≤Nmax; and    -   transmit the downlink data, to the terminal device, wherein the        downlink data is transmitted via a signal transmitted a number        of times equals to the actual number of downlink repetitions.

Clause 13. A method of receiving downlink data at a terminal in a mobilecommunications system, wherein the mobile communications systemcomprises a base station configured to communicate wireless signals toone or more terminal devices, the method comprising:

-   -   obtaining a maximum number of downlink repetitions “Nmax” for        downlink transmissions to the terminal wherein a number of        downlink repetitions indicates a number of times that the same        signal is transmitted to the terminal device;    -   setting the value of a decoding number of repetitions for        downlink data “Ndec” at a first value wherein 1≤Ndec≤Nmax; and    -   attempting to decode downlink data transmissions based on the        decoding number of repetitions for downlink data.

Clause 14. A method according to clause 13 wherein the method furthercomprises:

-   -   if the downlink data transmissions have not been successfully        decoded for the decoding number of repetitions for downlink        data:        -   if the Ndec is equal to the Nmax, detecting an unsuccessful            decoding of the downlink data transmissions; and        -   if the Ndec is not equal to the Nmax, selecting a new Ndec            which is greater than and not equal to the previous Ndec and            which is less than or equal to the Nmax, and returning to            the step of attempting to decode downlink data            transmissions.

Clause 15. A method according to clause 13 or 14 wherein the first valueis one.

Clause 16. A method according to clause 13 or 14 wherein the first valueis Nmax.

Clause 17. A method according to any of clauses 13 to 16, wherein thebase station is configured to communicate the wireless signals to theone or more terminal devices in a series of time sub-frames, whereinsub-frames comprise a first section for resource allocation and a secondsection for data transmission and wherein attempting to decode downlinkdata transmissions comprises:

-   -   attempting to decode resource allocation transmissions in the        first section of sub-frames; and    -   if resource allocation transmissions in the first section of        sub-frames have been successfully decoded, attempting to decode        the data transmissions in the second sections of sub-frames        based on the Ndec and on the decoded resource allocation        signals.

Clause 18. A method according to clause 17 wherein attempting to decoderesource allocation transmissions comprises attempting to decoderesource allocation transmissions based on a decoding number of downlinkrepetition for resource allocation signals “Ndec-ra” and wherein, ifresource allocation transmissions in the first section of sub-frameshave been successfully decoded, attempting to decode the datatransmissions in the second sections of sub-frames comprises attemptingto decode the data transmissions in the second section of sub-frameswith Ndec set to the Ndec-ra for the successful decoding of the resourceallocation transmissions.

Clause 19. A method according to clause 17 or 18 wherein the methodcomprises

-   -   obtaining a maximum number of downlink repetitions “Nmax-ra” for        downlink resource allocation transmissions to the terminal;

and wherein attempting to decode resource allocation transmissionscomprises:

-   -   attempting to decode resource allocation transmissions based on        a decoding number of downlink repetition for resource allocation        signals “Ndec-ra”, wherein the Ndec-ra is first set at a second        value such that 1≤Ndec-ra≤Nmax-ra;    -   if resource allocation signals in the first section of        sub-frames have not been successfully decoded:        -   if the Ndec-ra is equal to Nmax-ra, detecting an            unsuccessful decoding of the downlink resource allocation            transmissions;        -   if the Ndec-ra is not equal to Nmax-ra, selecting a new            Ndec-ra which is greater than and not equal to the previous            Ndec-ra and which is less than or equal to Nmax-ra, and            returning to the step of attempting to decode resource            allocation transmissions.

Clause 20. A method according to clause 19 wherein the second value isone.

Clause 21. A method according to clause 19 wherein the second value isNmax-ra.

Clause 22. A method according to any of clauses 19 to 21 wherein Nmax-rais equal to Nmax.

Clause 23. A method according to any of clauses clause 17 to 22, whereinthe sub-frames are grouped in a first time period for repeating resourceallocation signals and in a later second time period for repeating datasignals and wherein, if resource allocation transmissions aresuccessfully decoded for sub-frames of the first-time period, the stepof attempting to decode the data signals is carried out for sub-framesof the second time period.

Clause 24. A method according to clause 23 comprising, in the event thatresource allocation transmissions in the first section of sub-frameshave not been successfully decoded or that no resource allocationtransmissions for the terminal have been received, turning off areceiver for the terminal for the duration of the second period.

Clause 25. A terminal device for receiving downlink data at a terminalin a mobile communications system, wherein the mobile communicationssystem comprises a base station configured to communicate wirelesssignals to one or more terminal devices, the terminal device beingconfigured to:

-   -   obtain a maximum number of downlink repetitions “Nmax” for        downlink transmissions to the terminal wherein a number of        downlink repetitions indicates a number of times that the same        signal is transmitted to the terminal device;    -   set the value of a decoding number of repetitions for downlink        data “Ndec” at a first value wherein 1≤Ndec≤Nmax; and    -   attempt to decode downlink data transmissions based on the        decoding number of repetitions for downlink data.

Clause 26. Circuitry for a terminal device for receiving downlink dataat a terminal in a mobile communications system, wherein the mobilecommunications system comprises a base station configured to communicatewireless signals to one or more terminal devices, wherein the circuitrycomprises a controller element and a transceiver element configured tooperate together to:

-   -   obtain a maximum number of downlink repetitions “Nmax” for        downlink transmissions to the terminal wherein a number of        downlink repetitions indicates a number of times that the same        signal is transmitted to the terminal device;    -   set the value of a decoding number of repetitions for downlink        data “Ndec” at a first value wherein 1≤Ndec≤Nmax; and    -   attempt to decode downlink data transmissions based on the        decoding number of repetitions for downlink data.

Clause 27. A method of setting a maximum number of downlink repetitionsparameter for downlink transmissions in a mobile communications system,wherein the mobile communications system comprises a base stationconfigured to communicate wireless signals to one or more terminaldevices, the method comprising:

-   -   obtaining an upper limit “Nup” for the number of downlink        repetitions supported by a terminal device, wherein a number of        downlink repetitions indicates a number of times that the same        signal is transmitted to the terminal device;    -   determining, based on the upper limit, a maximum number of        downlink repetitions so that the maximum number of downlink        repetitions is less than or equal to the upper limit; and    -   transmitting an indicator of the maximum number of downlink        repetitions to a base station.

Clause 28. A method according to clause 27, wherein the determining ofthe maximum number of downlink repetitions is further based on a statusof the terminal device.

Clause 29. A method according to clause 27 or 28, wherein the status ofthe terminal device comprises a status of a power source for theterminal device.

Clause 30. A terminal device for setting a maximum number of downlinkrepetitions parameter for downlink transmissions in a mobilecommunications system, wherein the mobile communications systemcomprises a base station configured to communicate wireless signals toone or more terminal devices, the terminal device being configured to:

-   -   obtain an upper limit “Nup” for the number of downlink        repetitions supported by the terminal device, wherein a number        of downlink repetitions indicates a number of times that the        same signal is transmitted to the terminal device;    -   determine, based on the upper limit and on a status of the        terminal device, a maximum number of downlink repetitions so        that the maximum number of downlink repetitions is less than or        equal to the upper limit; and    -   transmit an indicator of the maximum number of downlink        repetitions to a base station.

Clause 31. Circuitry for a terminal device for setting a maximum numberof downlink repetitions parameter for downlink transmissions in a mobilecommunications system, wherein the mobile communications systemcomprises a base station configured to communicate wireless signals toone or more terminal devices, wherein the circuitry comprises acontroller element and a transceiver element configured to operatetogether to:

-   -   obtain an upper limit “Nup” for the number of downlink        repetitions supported by the terminal device, wherein a number        of downlink repetitions indicates a number of times that the        same signal is transmitted to the terminal device;    -   determine, based on the upper limit and on a status of the        terminal device, a maximum number of downlink repetitions so        that the maximum number of downlink repetitions is less than or        equal to the upper limit; and    -   transmit an indicator of the maximum number of downlink        repetitions to a base station.

Clause 32. A wireless telecommunication system comprising:

-   -   A terminal device according to clause 25 or 30; and    -   A base station according to clause 11.

Clause 33. Computer software which, when executed by a computer, causesthe computer to perform the method of any one of Clause 1 to Clause 10,Clause 13 to Clause 24 and Clause 27 to Clause 29.

Clause 34. A storage medium which stores computer software according toClause 33.

Clause 35. Any preceding Clause wherein the terminal devices and thebase station are operable to communicate at least one of: a 3GPPcommunication protocol, an LTE communication protocol, a 4Gcommunication protocol.

REFERENCES

-   [1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based    radio access”, John-   Wiley and Sons, 2009-   [2] ETSI TS 136 211 V11.5.0 (2014-01)/3GPP TS 36.211 version 11.5.0    Release 11-   [3] ETSI TS 136 212 V11.4.0 (2014-01)/3GPP TS 36.212 version 11.4.0    Release 11-   [4] ETSI TS 136 213 V11.6.0 (2014-03)/3GPP TS 36.213 version 11.6.0    Release 11-   [5] ETSI TS 136 321 V11.5.0 (2014-03)/3GPP TS 36.321 version 11.5.0    Release 11-   [6] ETSI TS 136 331 V12.3.0 (2014-09)/3GPP TS 36.331 version 12.3.0    Release 12-   [7] R1-124517 3GPP TSG-RAN1#70bis, San Diego, Calif., USA, 8-12 Oct.    2012

What is claimed is:
 1. A method of transmitting downlink data in amobile communications system, wherein the mobile communications systemcomprises a base station configured to communicate wireless signals toone or more terminal devices, the method comprising: receiving anindicator of a maximum number of downlink repetitions (Nmax) currentlyaccepted by a terminal device, wherein a number of downlink repetitionsindicates a number of times that a same signal is transmitted to theterminal device; deciding whether to transmit the downlink data to theterminal device based on a type of the downlink data; setting, inresponse to deciding to transmit the downlink data, an actual number ofdownlink repetitions (Ntx) so that the actual number of downlinkrepetitions Ntx satisfies a condition 1≤Ntx≤Nmax; setting, in responseto deciding not to transmit the downlink data, the actual number ofdownlink repetitions Ntx to zero; and transmitting the downlink data, tothe terminal device, via a signal transmitted a number of times equal tothe actual number of downlink repetitions Ntx.
 2. The method accordingto claim 1, wherein the setting of the actual number of downlinkrepetition Ntx is based on the type of the downlink data.
 3. The methodaccording to claim 2, wherein the type of the downlink data comprises apriority level for the downlink data.
 4. The method according to claim2, wherein the type of the downlink data is at least partially derivedfrom a type of service or application requesting the data transmission.5. The method according to claim 1, further comprising: retrieving areference number of downlink repetitions for the terminal device,wherein the setting of the actual number of downlink repetitions Ntx isbased on a comparison between the maximum number of downlink repetitionsNmax currently accepted by the terminal device and the reference numberof downlink repetitions.
 6. The method according to claim 1, wherein thebase station is configured to communicate the wireless signals to theone or more terminal devices in a series of sub-frames, sub-framescomprise a first section for resource allocation and a second sectionfor data transmission, and transmitting the downlink data to theterminal device comprises: transmitting a resource allocation messagefor the downlink data and for the terminal device via a first set of oneor more sub-frames in the first section; and subsequently transmittingthe downlink data in a second set of N sub-frames in the second section,wherein N is the actual number of repetitions.
 7. The method accordingto claim 6, wherein the sub-frames are grouped in a first time periodfor repeating resource allocation signals and in a second time periodfor repeating data signals, the first set of one or more sub-framesconsists of adjacent sub-frames starting at the start of the first timeperiod, and the second set of one or more sub-frames consists ofadjacent sub-frames starting at the start of the second time period. 8.The method according to claim 6, wherein the first set of one or moresub-frames consists of N sub-frames.
 9. The method according to claim 1wherein the actual number of downlink repetitions Ntx is set based onindications of success for past transmissions to the terminal device.10. Circuitry for a base station for transmitting downlink data in amobile communications system, wherein the base station is configured tocommunicate wireless signals to one or more terminal devices, thecircuitry comprising: controller circuitry and transceiver circuitryconfigured to operate together to: receive an indicator of a maximumnumber of downlink repetitions (Nmax) supported by a terminal device,wherein a number of downlink repetitions indicates a number of timesthat a same signal is transmitted to the terminal device; decide whetherto transmit the downlink data to the terminal device based on a type ofthe downlink data; set, in response to deciding to transmit the downlinkdata, an actual number of downlink repetitions (Ntx) so that the actualnumber of downlink repetitions Ntx satisfies a condition 1≤Ntx≤Nmax;set, in response to deciding not to transmit the downlink data theactual number of downlink repetitions Ntx to zero; and, transmit thedownlink data, to the terminal device, via a signal transmitted a numberof times equal to the actual number of downlink repetitions Ntx.
 11. Amethod of receiving downlink data at a terminal device in a mobilecommunications system, wherein the mobile communications systemcomprises a base station configured to communicate wireless signals toone or more terminal devices, the method comprising: obtaining a maximumnumber of downlink repetitions (Nmax) for downlink transmissions to theterminal device, wherein a number of downlink repetitions indicates anumber of times that a same signal is transmitted to the terminaldevice; setting a decoding number of repetitions for do link data (Ndec)at a first value, wherein 1≤Ndec≤Nmax; attempting to decode downlinkdata transmissions based on the decoding number of repetitions fordownlink data Ndec; and in response to the downlink data transmissionsbeing not successfully decoded: detecting, in response to the Ndec beingequal to the Nmax, an unsuccessful decoding of the downlink datatransmissions; and in response to the Ndec being less than the Nmax,selecting a new Ndec which is greater than the previous Ndec and whichis less than or equal to the Nmax, and again attempting to decodedownlink data transmissions.
 12. The method according to claim 11,wherein the first value is one.
 13. The method according to claim 11,wherein the first value is Nmax.
 14. The method according to claim 11,wherein the base station is configured to communicate the wirelesssignals to the one or more terminal devices in a series of sub-frames,sub-frames comprise a first section for resource allocation and a secondsection for data transmission, and the attempting to decode the downlinkdata transmissions comprises: attempting to decode resource allocationtransmissions in the first section of sub-frames; and attempting, if theresource allocation transmissions in the first section of sub-frameshave been successfully decoded, to decode the data transmissions in thesecond sections of sub-frames based on the Ndec and on the decodedresource allocation signals.
 15. A method according to claim 14, whereinthe attempting to decode the resource allocation transmissions is basedon a decoding number of downlink repetition for resource allocationsignals (Ndec-ra), and if resource allocation transmissions in the firstsection of sub-frames have been successfully decoded, the attempting todecode the data transmissions in the second sections of sub-framescomprises attempting to decode the data transmissions in the secondsection of sub-frames with Ndec set to the Ndec-ra for the successfuldecoding of the resource allocation transmissions.
 16. The methodaccording to claim 14, wherein the method comprises obtaining a maximumnumber of downlink repetitions (Nmax-ra) for downlink resourceallocation transmissions to the terminal, and the attempting to decodethe resource allocation transmissions comprises: attempting to decodethe resource allocation transmissions based on a decoding number ofdownlink repetition for resource allocation signals (Ndec-ra), whereinthe Ndec-ra is first set at a second value such that 1≤Ndec-ra≤Nmax-ra;if resource allocation signals in the first section of sub-frames havenot been successfully decoded: detecting, if the Ndec-ra is equal toNmax-ra, an unsuccessful decoding of the downlink resource allocationtransmissions; and if the Ndec-ra is not equal to Nmax-ra, selecting anew Ndec-ra which is greater than the previous Ndec-ra and which is lessthan or equal to Nmax-ra, and again attempting to decode the resourceallocation transmissions.
 17. The method according to claim 16, whereinthe second value is one.
 18. The method according to claim 16, whereinthe second value is Nmax-ra.
 19. The method according to claim 16,wherein Nmax-ra is equal to Nmax.
 20. The method according to claim 14,wherein the sub-frames are grouped in a first time period for repeatingresource allocation signals and in a later second time period forrepeating data signals, and if resource allocation transmissions aresuccessfully decoded for sub-frames of the first-time period, theattempting to decode the data signals is carried out for sub-frames ofthe second time period.
 21. The method according to claim 20, furthercomprising, in an event that resource allocation transmissions in thefirst section of sub-frames have not been successfully decoded or thatno resource allocation transmissions for the terminal have beenreceived, turning off a receiver for the terminal device for a durationof the second period.
 22. A terminal device for receiving downlink datain a mobile communications system, wherein the mobile communicationssystem comprises a base station configured to communicate wirelesssignals to one or more terminal devices, the terminal device comprising:circuitry configured to: obtain a maximum number of downlink repetitions(Nmax) for downlink transmissions to the terminal device, wherein anumber of downlink repetitions indicates a number of times that a samesignal is transmitted to the terminal device; set a decoding number ofrepetitions for downlink data (Ndec) at a first value wherein1≤Ndec≤Nmax; attempt to decode downlink data transmissions based on thedecoding number of repetitions for downlink data Ndec; and in responseto the downlink data transmissions being not successfully decoded;detect, in response to the Ndec being equal to the Nmax, an unsuccessfuldecoding of the downlink data transmissions; and in response to the Ndecbeing less than the Nmax, select a new Ndec which is greater than theprevious Ndec and which is less than or equal to the Nmax, and againattempt to decode downlink data transmissions.